This invention relates to a process for preparing certain bridged monocyclopentadienyl Group 4 metal complexes. More particularly, this invention relates to such a process involving nucleophilic substitution of corresponding bis(cyclopentadienyl) Group 4 metal complexes. Further, the invention relates to bis(cyclopentadienyl) Group 4 metal complexes, to a process for preparing the same, and to an addition polymerization process using a catalyst comprising the same complex and an activating cocatalyst.
Monocyclopentadienyl Group 4 metal complexes, particularly those wherein the cyclopentadienyl derivative group is part of a bridging ligand group are known and useful in catalyst compositions for addition polymerizations, particularly in polymerizing and interpolymerizing olefins, diolefins, vinyl-aromatic monomers, and/or acetylenically unsaturated monomers.
Bridged monocyclopentadienyl Group 4 metal complexes, including those which also contain at least one hydrocarbon group other than a cyclopentadienyl covalently bonded to the Group 4 metal, are disclosed in EP-A-0,416,815, EP-A-0,418,044, U.S. Pat. No. 5,026,798, WO 92/00333 and WO 93/19104 (corresponding to U.S. Ser. No. 8003, filed Jan. 21, 1993 now U.S. Pat. No. 5,374,696).
EP-A-0,418,044, in example 3 and WO 92/00333 teach that bridged monocyclopentadienyl dihydrocarbyl Group 4 metal(+4) complexes can be prepared by hydrocarbylating the corresponding bridged monocyclopentadienyl Group 4 metal(+4) dihalide complexes with a Grignard, lithium, sodium or potassium salt of the hydrocarbyl ligand. The dihalide complexes in themselves are prepared by reacting the Group 4 metal(+4) tetrahalide with a dianionic derivative of the bridging monocyclopentadienyl ligand. Alternative methods to prepare these dihalide complexes are disclosed in EP-A-0,416,815 and EP-A-0,514,828 which require reacting an ether adduct of a transition metal(+3) trihalide compound with the dianionic derivative of the cyclopentadienyl ligand, followed by contacting the resulting complex with a non-interfering oxidizing agent, such as for example AgCl (EP-A-0,416,815) or an organic halide (EP-A-0,514,828) to raise the oxidation state of the metal to form the desired metal(+4) dihalide complex.
The bridged monocyclopentadienyl monohydrocarbyl metal(+3) coordination complexes can be prepared by hydrocarbylating the corresponding bridged monocyclopentadienyl metal(+3) monohalide coordination complexes with a Grignard, lithium, sodium or potassium salt of the hydrocarbyl ligand. The bridged monocyclopentadienyl metal(+3) monohalide complexes themselves are prepared by reacting a Group 4 metal(+3) trihalide compound, in the form of an ether adduct, with a dianionic derivative of the bridging monocyclopentadienyl ligand. Alternatively, the bridged monocyclopentadienyl monohydrocarbyl metal(+3) complexes are prepared by monohydrocarbylating the corresponding bridged monocyclopentadienyl metal(+4) dihalide complexes with a Grignard, lithium, sodium or potassium salt of the hydrocarbyl ligand, followed by reducing with a metal such as magnesium. These synthesis methods are described in WO 93/19104 (corresponding to U.S. Ser. No. 8003, filed Jan. 21, 1993).
All of the synthesis methods described hereinbefore start from Group 4 metal tri- or tetrahalide compounds which are corrosive, toxic, and air and moisture sensitive. In the presence of moisture these compounds liberate HCl. In order to facilitate handling thereof, prior to the reaction step the transition metal tri- or tetrahalide compound is typically converted to its ether-adduct in a separate step with, for example, THF or diethyl ether. This adduct formation step in itself is difficult to perform on a large scale due to the high exothermicity of the reaction, requiring efficient cooling and low to very low temperatures and careful addition to prevent Lewis acid-catalyzed cleavage of the ether molecule, and an inert atmosphere. The adduct is usually recovered before it is reacted with the dianionic derivative of the bridged monocyclopentadienyl ligand compound.
In J. Organometal. Chem. 1976, 110, 321, A. Dormond et al. describe the reaction between bis(cyclopentadienyl) titanium(+4) dichloride and a dianionic derivative of a bridged biscyclopentadienyl ligand, Na.sub.2 C.sub.5 H.sub.4 (CH.sub.2).sub.3 C.sub.5 H.sub.4 !, to form a mixture of di-.eta..sup.5 -C.sub.5 H.sub.4 (CH.sub.2).sub.3 C.sub.5 H.sub.4 !Ti (.eta..sup.1 -C.sub.5 H.sub.5).sub.2 and (.eta..sup.5 -C.sub.5 H.sub.5).sub.2 Ti di-.eta..sup.1 -C.sub.5 H.sub.4 (CH.sub.2).sub.3 C.sub.5 H.sub.4 !. Dormond et al. further disclose that bis(cyclopentadienyl) titanium(+4) bis(phenyl) when attacked by phenyl lithium forms the complex Cp.sub.2 TiPh.sub.3 !.sup.- Li.sup.+ which ultimately decomposes to CpTiPh.sub.2, CpLi and a phenyl radical.
DE-A-3,936,096 generically discloses the reaction between MeX'.sub.q.(solv').sub.r, wherein Me could be Ti or Zr, X' could be Cl, Br, I, --OOCR', --OR', --NR'.sub.2, -cyclopentadienyl, solv' is ether or tert. amine, q is 2-5, and r is 0-3, with a dialkali metal- or digrignard organo compound to form homoleptic metallacyclic organometal compounds.
It would be desirable to develop an improved process to prepare mono- or dihydrocarbyl derivatives of bridged monocyclopentadienyl Group 4 metal complexes which process avoids the use of the corrosive, toxic, and air and moisture sensitive metal tetrahalide or trihalide starting compounds, and avoids the formation of an ether adduct.
It would also be desirable to provide a process for the preparation of monohydrocarbyl derivatives of bridged monocyclopentadienyl Group 4 metal(+3) complexes which process avoids the use of any Group 4 metal(+4) compound or complex and thus requires fewer steps, such as a reduction step from the +4 oxidation state to the +3 oxidation state.
It would yet further be desirable to provide certain novel stable bis(cyclopentadienyl) metal complexes which enable the desired mono- or dihydrocarbyl derivatives of bridged monocyclopentadienyl Group 4 metal complexes to be prepared. It would be furthermore desirable to provide certain novel stable bis(cyclopentadienyl) metal complexes which are useful in catalyst compositions for addition polymerization processes.